Merge Maestro into Decodex monorepo

[yvette-carlisle]

Summary

• integrate the former Maestro runtime under apps/decodex inside the Decodex workspace
• keep the public Astro site as the static site surface under site/
• align release, language checks, dependency style, and Makefile task structure with the merged Decodex layout
• move Decodex plugin skills under plugins/decodex and remove obsolete rulesets/hash release step

Verification

• actionlint .github/workflows/*.yml
• taplo fmt --check Makefile.toml
• cargo make check-site
• cargo make checks